Crystal and Electronic Structures of a New Hexagonal Silicide Sc38co144si97

Abstract

Sc 38 Co 144 Si 97 was prepared from the elements by arc melting under argon and subsequent annealing at 800 o C for 350 h. Single-crystal X-ray diffraction reveals Sc 38 Co 144 Si 97 to crystallize in a new hexagonal structure type: Pearson's symbol hP 279, space group P 6 3 /m, a = 33.624(7), c = 3.639(1) Å. The crystal structure of Sc 38 Co 144 Si 97 can be considered as a 2D intergrowth of three kinds of fragments of simpler structure types: hexagons and quadrilaterals with the arrangements of the Sc 6 Co 30 Si 19 type and triangles with the arrangement of the Gd 4 Co 13 (Si, P) 9 type. Quantum chemical calculations have been performed to analyze the electronic structure and provide deeper insight into the structure-property relationships. The Extended Hückel (EH) calculation indicates that Co in Sc 38 Co 144 Si 97 adopts close to a d 10 configuration owing to the covalent interaction with Si. The Co–Si bonds provide the highest contribution to the total orbital interactions.

Keywords: crystal structure, Electronic structure, Silicides, Scandium